Is there a neural basis for sensorimotor impairments in non-specific low back pain?

Globally, low back pain causes more disability than any other condition. Unfortunately, most people will experience this condition at some point in their lives. Treating low back pain is very challenging because in up to 85% of cases, the pain cannot be attributed to a specific spinal pathology, such as a fracture or herniated disc. This is called ‘non-specific low back pain’ (NSLBP). The fact that most interventions tackle NSLBP at the level of the spine itself might explain why they only have small to modest effects. Current thinking emphasizes the need to look ‘beyond’ the spine and search for other mechanisms that underlie NSLBP, for instance at the level of the brain.

Over the past few years, studies revealed that NSLBP is characterized by sensorimotor impairments at the lower back. For instance, individuals with NSLBP were less accurate in judging from a photo whether a person had his trunk rotated to the left or to the right, although they performed normally on a similar task of the hand [1]. They also made more errors when asked to name the letter drawn on the skin of their lower back, and when re-positioning their lower back to a predetermined position [2, 3]. Also, our research group showed that they rely less on proprioceptive signals from the lower back to control their upright posture [4]. These findings might suggest that patients with NSLBP are less able to process tactile and proprioceptive signals from the lower back in the brain. However, it remains largely unclear whether the sensorimotor impairments seen in patients with NSLBP are also present at the level of the brain.

Therefore, we summarized findings from all available fMRI-studies (n=9) investigating brain activation related to sensory processing and movement performance in individuals with NSLBP [5]. In contrast to other reviews, we focused on studies that did not aim to induce pain by applying sensory stimuli or movements. As such, we specifically targeted studies that purely investigated sensorimotor processing (vs. pain) in the brain.

First, compared to healthy individuals, patients with NSLBP showed decreased brain activation during the processing of tactile-proprioceptive signals from the lower back [6], and while imagining daily life activities [7]. These decreases were found in brain areas important for higher-order sensory processing, motor planning and postural control. Therefore, we speculate that these brain changes might contribute to the impaired sensorimotor behavior seen in individuals with NSLBP. Moreover, patients with NSLBP exhibited increased brain responses in numerous brain areas during the processing of pressure stimuli on the thumb [8], and during imagining daily life activities [7] compared to healthy individuals. Furthermore, a case study revealed that a patient with NSLBP showed an initially widespread over-activation during contracting the abdominal muscles, which decreased drastically after one session of pain education [9]. These results of widespread over-activation were often interpreted as ‘abnormal pain processing’ in NSLBP, because most of the identified brain regions fell within the so-called ‘pain matrix’. However, do these results really suggest that patients with NSLBP show abnormal pain processing? Or is there an alternative explanation?

Recent papers shed new light on this issue. Apparently, not only nociceptive inputs, but also non-painful somatosensory, visual and auditory stimuli can elicit responses in the ‘pain matrix’ [10]. Moreover, ‘pain matrix’ responses to noxious stimuli become larger when the stimuli are unpredictable or novel [11]. These findings propose that the ‘pain matrix’ does not solely present a cortical representation of pain. Rather, the networks that contribute to the matrix act as a defense system that detects, shifts attention towards and reacts to salient sensory inputs [12, 13]. Salient sensory inputs can be defined as “inputs that stand out relative to their environment”, because they contrast greatly from their surroundings, are new or diverge from expectations based on experience.

These insights might help to re-interpret the increased sensorimotor-evoked brain responses within the so-called ‘pain matrix’ in NSLBP. They suggest that individuals with NSLBP are over-responsive or over-attentive towards sensory inputs that potentially signal ‘danger to the lower back’ and require action to protect the spine. Such protective responses have been shown in patients with NSLBP and although they initially might be adaptive (e.g., over-activating trunk muscles during bending or walking to prevent movement-related pain), they often become maladaptive, leading to recurrences or even chronic pain.

All in all, the results from our review highlight that, when treating NSLBP, we need to look further than impairments at the spinal level. We need to bear in mind that NSLBP might need to be tackled at the level of the brain. These findings will likely contribute to the development of novel interventions that specifically target brain changes in NSLBP. Examples are motor imagery, kinesthetic imagery, sensory discrimination training, combining exercise therapy with peripheral or transcranial magnetic stimulation, and educating patients on pain physiology to reduce the perceived threat related to movement. Perhaps, such developments might even be useful for improving treatments of other (musculoskeletal) conditions.

About Nina Goossens

Nina is a PhD researcher at the Musculoskeletal Rehabilitation Research Group, KU Leuven, Belgium. In her PhD project, (co-)supervised by prof. dr. Simon Brumagne, prof. dr. Karen Caeyenberghs and dr. Lotte Janssens, she currently unravels underlying mechanisms of proprioceptive and postural control deficits in patients with NSLBP. By combining fMRI with local muscle vibration [14], she examines how proprioceptive signals are processed centrally (at brain level) and how this central proprioceptive processing is related to postural control deficits in patients with NSLBP and healthy individuals.

References

Bray H, Moseley GL. Disrupted working body schema of the trunk in people with back pain. Br J Sports Med 2011; 45; 168-73.

Are you young with CRPS? We need your help!

Young people with CRPS and parents/caregivers are needed for research being conducted at Bath University

The study involves asking young people (14-25 years) with CRPS and parents of young people with CRPS to complete a 20-25 online survey which asks them to think about their future. Study recruitment is being conducted separately for both young people and parents. Please email crpsstories@bath.ac.uk if you would like to take part. Participants will be paid for their time.

PainAdelaide 2019

For you interstaters / internationallers – it is the day after Womad so combine a trip to the Festival City with one of the world’s truly great music festivals. Put it in your diary and we will let you know as soon as registration is up and running.

It’s impossible to slip your disc!

Lorimer Moseley answering the question “What is the thing that annoys you most when we talk about back pain?”

Online survey on bodily changes, sensations, and mood in people with chronic pain

How do CRPS and other chronic pain conditions affect bodily functions, sensations, and mood? Help CRPS researcher Janet Bultitude find out by responding to her survey.

The survey is aimed at people with CRPS, people with chronic pain conditions other than CRPS, and people without any chronic pain condition. The survey takes approximately 20 minutes and the responses are anonymous.

Prof Paul Hodges on pain and altered movement

Am I safe to move?

Listen to Lorimer Moseley talk to Karim Khan on new understanding of pain and focusing on the patient.

Understanding Pain

Regular physical activity is important for our health and well-being. Recent evidence suggests that independent of being physically active, limiting the duration of sedentary behavior, such as sitting or lying down, is important to reduce the risk for cardiovascular disease, diabetes, cancer and all-cause mortality (Biswas et al. 2015). Advances in wearable sensors provide a […]

We don’t normally have to think about our breathing and that’s because breathing is handled by a subconscious part of the brain called the medulla. The medulla automatically controls our breathing as well as our heart rate and blood pressure (Del Negro et al. 2018). It sends neural signals to the breathing muscles to activate them […]

Got an event or meeting you want to promote?

We might be able to help you spread the word. Tell us in an email,

Who is the convenor?
Who is the contact person?
Where and when is it?
Is it non-profit, an association meeting or a commercial venture?
What is the objective?
Who are you wanting to attend?
Where can people go to find out more?

Then contact Heidi@bodyinmind.org

BiM will no longer have comments

Dear BiM Community
We have come to the difficult decision to stop comments as this feature is no longer serving its intended function for the wider readership of BiM. Our aim is to facilitate and disseminate good clinical science research, the comments section were for folks to engage with this research constructively and not promote individual views or therapies. We feel this function is now not being fulfilled.

Archives

Archives

Looking for information?

We often get people writing in about their particular conditions asking for more information and help. Unfortunately we get too many to be able to respond personally. We do not publish these comments for privacy reasons and we cannot offer treatment advice.

All blog posts should be attributed to their author, not to BodyInMind. That is, BodyInMind wants authors to say what they really think, not what they think BodyInMind thinks they should think. Think about that!

Subscribe!

All blog posts should be attributed to their author, not to BodyInMind. That is, BodyInMind wants authors to say what they really think, not what they think BodyInMind thinks they should think. Think about that!

We aim to facilitate and disseminate good clinical science research. We love comments that engage with the research and are constructive and respectful. We do not prescribe treatments. Promotion of your particular therapy in the comments section is not appropriate here either - that is not the point of BiM. Finally, all the comments that are made reflect the views of the person who made them and are not endorsed by BiM or members of the BiM research group.